The complement system is considered an ancient part of the immune system, which serves to discriminate self and non-self (see, for example, Rother et al. (Eds.), The Complement System, Second Edition (Springer-Verlag 1998), Morely and Walport, The Complement Factsbook (Academic Press 1999), and Morgan (Ed.), Complement Methods and Protocols (Humana Press, Inc. 2000)). Although the complement system plays an important role in providing resistance to infections, an inappropriate activation of complement can result in a variety of disorders.
There are two main pathways for complement activation, which are known as the classical and alternative pathways. Both pathways comprise a cascade of enzyme activation, which leads to the production of a terminal membrane attack complex that targets immune complexes or microorganisms. The alternative pathway is activated by the chance binding of C3b with the surface of a microorganism. The classical pathway is the principal antibody-directed mechanism for the activation of complement. C1, the first enzyme complex in the classical pathway, is a pentamolecular complex consisting of a single C1q molecule, and two C1r and C1s molecules. In the classical pathway, an antibody binds with C1q, which causes the activation of the C1r molecules. These activated proteins then cleave the C1s molecules to form active C1s serine proteases, which act on the next two components of the classical complement pathway, C4 and C2. Cleaved portions of these complement proteins, known as C4b and C2a, then form C3 convertase, which goes on to cleave the next component in the cascade, C3. Thus, C1s plays a key role, because one C1s molecule can generate multiple C4b molecules, which have an amplification effect on the system.
Molecules that inhibit complement may be beneficial for treatment of diseases in which complement activation has been shown to occur, such as adult respiratory distress syndrome, ischemia-reperfusion injury (myocardial infarct, stroke, skeletal muscle, lung inflammation), hyperacute rejection (transplantation), sepsis, cardiopulmonary bypass, burns, wound healing, asthma, restenosis, multiple organ dysfunction syndrome, trauma, hemorrhagic shock, Guillain-Barre syndrome, paroxysmal nocturnal hemoglobinuria, glomerulonephritis, systemic lupus erythematosus, rheumatoid arthritis, infertility, Alzheimer's disease, organ rejection, myasthenia gravis, multiple sclerosis, platelet storage, serum sickness, various hemolytic anemias, and hemodialysis See, for example, Vogt, Trends Pharm. Sci. 6:114 (1985), and Makrides, Pharm. Rev. 50:59 (1998).
Many different types of compounds have been found to be inhibitors of classical complement, including diamines, amino acids and their derivatives, polynucleotides, polyanions, pyridinium sulphonylfluorides and phenothiazines (see, for example, Ashghar, Pharmac. Rev. 36:223 (1984)). Peptide inhibitors are exemplified by amino acid sequences that mimic the C1 fixing sequences of IgG, glutathione, and leupeptin (see, for example, Boackle et al., Nature 282:742 (1979); Takada et al., Immunology 34:509 (1979)). A tripeptide based on C-terminal sequences of C3a and C5a has been shown to be a substrate for C4b2a, CVFBb and C1s, while substrate-like inhibitors of C3 convertase have also been prepared (see, for example, Andreatta et al., In Enzyme Inhibitors, Brodbeck (Ed.), pages 261–272 (1981); Caporale et al., J. Immun. 126:1963 (1981)).
Few compounds have been found to inhibit the alternative pathway. Complestatin, a microbial product believed to bind to factor B is one example of such an inhibitory compound (Kaneko et al., J. Immun. 124:1194 (1980)). Many inhibitors described above require relatively high concentrations, and lack specificity.
Protein inhibitors of complement have been described more recently, and include: soluble complement receptor (sCRI), a humanized monoclonal antibody to C5, and BD001, a recently described protein derived from a leech, which inhibits C1s (Liszewski and Atkinson, Exp Opin, Invest. Drugs 7:323 (1998); Seale and Finney, International Publication No. WO99/36439). Seale and Finney reported that BD001 has the following amino acid sequence:
(SEQ ID NO:1)AKKKLPKCQK QEDCGSWDLK CNNVTKKCEC RNQVCGRGCP KERYQRDKYG CRKCLCKGCD GFKCRLGCTY GFKTDKKGCE AFCTCNTKET ACVNIWCTDP YKCNPESGRC EDPNEEYEYD YE
The discovery of new C1s-inhibitory peptides and polypeptides fulfills a need in the art by providing new compositions useful in diagnosis and therapy. The present invention provides such polypeptides for these and other uses that should be apparent to those skilled in the art from the teachings herein.